This program project renewal application represents a continuation of a multi-investigator approach to study immunologic and pathologic mechanisms that contribute to our understanding of pulmonary disease. The program consists of 5 projects and 3 cores. The projects can be grouped into 3 categories: 1) Acute pathologic and immunopathologic reactions, 2) Chronic pathologic and immunopathologic reactions, and 3) Host defense and immunologic responses. In the first category, emphasis will be placed on the effect of microbial toxins on the lung as consequence of pneumonia. In addition, mechanisms of neutrophil sequestration and neutropenia will be studied in relation to shock lung. In the second category, the mechanisms of tissue damage in allergic granulomas will be analyzed. Emphasis will be placed on molecular mediators including lymphokines, hydrolases, immunoglobulins and metabolic products. The third group will undertake studies on the response of the lung to antigenic challenge with respect to the role of bronchus associated tissue and the hilar lymph node complex. Three core units will support this program: 1) Electron Microscope Core, 2) Preparatory Biochemistry Core, and 3) Administrative Core.